Do positrons exist? Did they exist before the first observation of a positron? Did they first come into existence when Dirac’s mathematics indicated that there might be such particles?

One of the curiosities about particle physics is that, decade after decade, we go through the same discovery sequence. In order to make the math work out, it is convenient to hypothesize a new particle. For instance, the Higgs boson. Apparatus, of which the Large Hadron Collider is the most recent incarnation, is built to look for that particle. Tremendous amounts of data are produced, so sophisticated event filters are built into the apparatus, both physical filters and logical filters, to concentrate attention on just the sorts of events that will be indicative of the particle being searched for. And … the particle is observed.

I can understand that discovery process in regard to bosons. Bosons do not have an exclusion principle — they are, in essence, like resonances. Any number and variety of bosons can stack up “in one place”. If we tune our ear, or a sophisticated filter, to hear just particular resonances, and listen to white noise (the universe), we will sooner or later observe that resonance. No problem! There are benefits to this discovery process as a worthwhile activity.

I have stood at the ocean shore, video recording waves after they have crossed a million meters of open ocean, trying to get a handle on their frequencies. Arrivals of ocean waves, at the scale of 1-2 meters, are not evenly spaced. Arrival times between waves on one typical day were 4 to 13 seconds, with a mean of 8 seconds, and a standard deviation of 2.8 seconds. There were also many small wavelets to be seen, running between the big waves, some running at an angle of up to 30-40 degrees from the big waves. If I built a wavelet detector to look for wavelet events which are in a certain energy density range, say 50 cm height, and are polarized at say 48-52 degrees from the big waves, I’m sure those would be detected if I waited long enough. The study of waves is fascinating. (An aside: when I go on vacation, I tell some people that I’m going to be studying wave mechanics. Science is serious!)

But fermions, which do obey an exclusion principle, are much more like “real particles”. Once a fermion, always a fermion! Unless, of course, an electron and a positron happen to come into contact.

Best wishes,
Ken Roberts
06-March-2014